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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Z. Hu 3 Internet-Draft L. Zhu 4 Intended status: Standards Track J. Heidemann 5 Expires: March 21, 2016 USC/Information Sciences 6 Institute 7 A. Mankin 8 D. Wessels 9 Verisign Labs 10 P. Hoffman 11 ICANN 12 September 18, 2015 14 DNS over TLS: Initiation and Performance Considerations 15 draft-ietf-dprive-dns-over-tls-00 17 Abstract 19 This document describes the use of TLS to provide privacy for DNS. 20 Encryption provided by TLS eliminates opportunities for eavesdropping 21 on DNS queries in the network, such as discussed in RFC 7258. In 22 addition, this document specifies two usage profiles for DNS-over-TLS 23 and provides advice on performance considerations to minimize 24 overhead from using TCP and TLS with DNS. 26 Note: this document was formerly named 27 draft-ietf-dprive-start-tls-for-dns. Its name has been changed to 28 better describe the mechanism now used. Please refer to working 29 group archives under the former name for history and previous 30 discussion. [RFC Editor: please remove this paragraph prior to 31 publication] 33 Status of this Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at http://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on March 21, 2016. 50 Copyright Notice 52 Copyright (c) 2015 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 68 2. Reserved Words . . . . . . . . . . . . . . . . . . . . . . . . 4 69 3. Establishing and Managing DNS-over-TLS Sessions . . . . . . . 4 70 3.1. Session Initiation . . . . . . . . . . . . . . . . . . . . 4 71 3.2. TLS Handshake and Authentication . . . . . . . . . . . . . 4 72 3.3. Transmitting and Receiving Messages . . . . . . . . . . . 5 73 3.4. Connection Reuse, Close and Reestablishment . . . . . . . 5 74 4. Usage Profiles . . . . . . . . . . . . . . . . . . . . . . . . 6 75 4.1. Opportunistic Privacy Profile . . . . . . . . . . . . . . 7 76 4.2. Pre-Deployed Profile . . . . . . . . . . . . . . . . . . . 7 77 5. Performance Considerations . . . . . . . . . . . . . . . . . . 8 78 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 79 7. Design Evolution . . . . . . . . . . . . . . . . . . . . . . . 9 80 8. Implementation Status . . . . . . . . . . . . . . . . . . . . 10 81 8.1. Unbound . . . . . . . . . . . . . . . . . . . . . . . . . 10 82 8.2. ldns . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 83 8.3. digit . . . . . . . . . . . . . . . . . . . . . . . . . . 11 84 8.4. getdns . . . . . . . . . . . . . . . . . . . . . . . . . . 11 85 9. Security Considerations . . . . . . . . . . . . . . . . . . . 11 86 10. Contributing Authors . . . . . . . . . . . . . . . . . . . . . 12 87 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 88 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 89 12.1. Normative References . . . . . . . . . . . . . . . . . . . 12 90 12.2. Informative References . . . . . . . . . . . . . . . . . . 13 91 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 93 1. Introduction 95 Today, nearly all DNS queries [RFC1034], [RFC1035] are sent 96 unencrypted, which makes them vulnerable to eavesdropping by an 97 attacker that has access to the network channel, reducing the privacy 98 of the querier. Recent news reports have elevated these concerns, 99 and recent IETF work has specified privacy considerations for DNS 100 [RFC7626]. 102 Prior work has addressed some aspects of DNS security, but until 103 recently there has been little work on privacy between a DNS client 104 and server. DNS Security Extensions (DNSSEC), [RFC4033] provide 105 _response integrity_ by defining mechanisms to cryptographically sign 106 zones, allowing end-users (or their first-hop resolver) to verify 107 replies are correct. By intention, DNSSEC does not protect request 108 and response privacy. Traditionally, either privacy was not 109 considered a requirement for DNS traffic, or it was assumed that 110 network traffic was sufficiently private, however these perceptions 111 are evolving due to recent events [RFC7258]. 113 Other work that has offered the potential to encrypt between DNS 114 clients and servers includes DNSCurve [dempsky-dnscurve], 115 ConfidentialDNS [I-D.confidentialdns] and IPSECA [I-D.ipseca]. In 116 addition to the present draft, the DPRIVE working group has recently 117 adopted a DNS-over-DTLS [draft-ietf-dprive-dnsodtls] proposal. 119 This document describes using DNS-over-TLS on a well-known port and 120 also offers advice on performance considerations to minimize 121 overheads from using TCP and TLS with DNS. 123 Initiation of DNS-over-TLS is very straightforward. By establishing 124 a connection over a well-known port, clients and servers expect and 125 agree to negotiate a TLS session to secure the channel. Deployment 126 will be gradual. Not all servers will support DNS-over-TLS and the 127 well-known port might be blocked by some firewalls. Clients will be 128 expected to keep track of servers that support TLS and those that 129 don't. Clients and servers will adhere to the TLS implementation 130 recommendations and security considerations of [RFC7525]. 132 The protocol described here works for any DNS client to server 133 communication using DNS-over-TCP. That is, it may be used for 134 queries and responses between stub clients and recursive servers as 135 well as between recursive clients and authoritative servers. 137 This document describes two profiles in Section 4 providing different 138 levels of assurance of privacy: an opportunistic privacy profile and 139 a pre-deployed profile. 141 An earlier version of this document described a technique for 142 upgrading a DNS-over-TCP connection to a DNS-over-TLS session with, 143 essentially, "STARTTLS for DNS". To simplify the protocol, this 144 document now only uses a well-known port to specify TLS use, omitting 145 the upgrade approach. The upgrade approach no longer appears in this 146 document, which now focuses exclusively on the use of a well-known 147 port for DNS-over-TLS. 149 2. Reserved Words 151 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 152 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 153 document are to be interpreted as described in RFC 2119 [RFC2119]. 155 3. Establishing and Managing DNS-over-TLS Sessions 157 3.1. Session Initiation 159 A DNS server that supports DNS-over-TLS SHOULD listen for and accept 160 TCP connections on a designated port TBD identified in Section 6. 162 DNS clients desiring privacy from DNS-over-TLS from a particular 163 server SHOULD establish a TCP connection to port TBD on the server. 164 Upon successful establishment of the TCP connection, client and 165 server SHOULD immediately initiate a TLS handshake using the 166 procedure described in [RFC5246]. 168 DNS clients SHOULD remember server IP addresses that don't support 169 DNS-over-TLS, including timeouts, connection refusals, and TLS 170 handshake failures, and not request DNS-over-TLS from them for a 171 reasonable period (such as one hour per server). DNS clients 172 following a pre-deployed privacy profile MAY be more aggressive about 173 retrying DNS-over-TLS connection failures. 175 3.2. TLS Handshake and Authentication 177 Once the DNS client succeeds in connecting via TCP on the well-known 178 port for DNS-over-TLS, it proceeds with the TLS handshake [RFC5246], 179 following the best practices specified in [RFC7525]). 181 The client will then authenticate the certificate, if required. DNS- 182 over-TLS does not propose new ideas for certificate authentication. 183 Depending on the privacy profile in use Section 4, the DNS client may 184 choose not to require authentication of the certificate, or it may 185 make use of a certificate that is part of the Certificate Authority 186 infrastructure [RFC5280] authenticated in the manner of HTTP/TLS 188 [RFC2818]. DANE [RFC6698] provides mechanisms to root certificate 189 trust with DNSSEC. The DNS queries in DANE authentication of the 190 certificate for DNS-over-TLS MAY be in the clear to avoid trust 191 recursion. 193 After TLS negotiation completes, the connection will be encrypted and 194 is now protected from eavesdropping. At this point, normal DNS 195 queries SHOULD take place. 197 3.3. Transmitting and Receiving Messages 199 All messages (requests and responses) in the established TLS session 200 MUST use the two-octet length field described in Section 4.2.2 of 201 [RFC1035]. For reasons of efficiency, DNS clients and servers SHOULD 202 transmit the two-octet length field, and the message described by 203 that length field, in a single TCP segment ([I-D.ietf-dnsop-5966bis], 204 Section 8). 206 In order to minimize latency, clients SHOULD pipeline multiple 207 queries over a TLS session. When a DNS client sends multiple queries 208 to a server, it should not wait for an outstanding reply before 209 sending the next query ([I-D.ietf-dnsop-5966bis], Section 6.2.1.1). 211 Since pipelined responses can arrive out-of-order, clients MUST match 212 responses to outstanding queries using the ID field and port number. 213 Failure by clients to properly match responses to outstanding queries 214 can have serious consequences for interoperability 215 ([I-D.ietf-dnsop-5966bis], Section 7). 217 3.4. Connection Reuse, Close and Reestablishment 219 For DNS clients that use library functions such as "gethostbyname()", 220 current implementations are known to open and close TCP connections 221 each DNS call. To avoid excess TCP connections, each with a single 222 query, clients SHOULD reuse a single TCP connection to the recursive 223 resolver. Alternatively they may prefer to use UDP to a DNS-over-TLS 224 enabled caching resolver on the same machine that then uses a system- 225 wide TCP connection to the recursive resolver. 227 In order to amortize TCP and TLS connection setup costs, clients and 228 servers SHOULD NOT immediately close a connection after each 229 response. Instead, clients and servers SHOULD reuse existing 230 connections for subsequent queries as long as they have sufficient 231 resources. In some cases, this means that clients and servers may 232 need to keep idle connections open for some amount of time. 234 Proper management of established and idle connections is important to 235 the healthy operation of a DNS server. An implementor of DNS-over- 236 TLS SHOULD follow best practices for DNS-over-TCP, as described in 237 [I-D.ietf-dnsop-5966bis]. Failure to do so may lead to resource 238 exhaustion and denial-of-service. 240 Whereas client and server implementations from the [RFC1035] era are 241 known to have poor TCP connection management, this document 242 stipulates that successful negotiation of TLS indicates the 243 willingness of both parties to keep idle DNS connections open, 244 independent of timeouts or other recommendations for DNS-over-TCP 245 without TLS. In other words, software implementing this protocol is 246 assumed to support idle, persistent connections and be prepared to 247 manage multiple, potentially long-lived TCP connections. 249 This document does not make specific recommendations for timeout 250 values on idle connections. Clients and servers should reuse and/or 251 close connections depending on the level of available resources. 252 Timeouts may be longer during periods of low activity and shorter 253 during periods of high activity. Current work in this area may also 254 assist DNS-over-TLS clients and servers select useful timeout values 255 [I-D.edns-tcp-keepalive] [tdns]. 257 Clients and servers that keep idle connections open MUST be robust to 258 termination of idle connection by either party. As with current DNS- 259 over-TCP, DNS servers MAY close the connection at any time (perhaps 260 due to resource constraints). As with current DNS-over-TCP, clients 261 MUST handle abrupt closes and be prepared to reestablish connections 262 and/or retry queries. 264 When reestablishing a DNS-over-TCP connection that was terminated, as 265 discussed in [I-D.ietf-dnsop-5966bis], TCP Fast Open [RFC7413] is of 266 benefit. DNS servers SHOULD enable fast TLS session resumption 267 [RFC5077] and this SHOULD be used when reestablishing connections. 269 When closing a connection, DNS servers SHOULD use the TLS close- 270 notify request to shift TCP TIME-WAIT state to the clients. 271 Additional requirements and guidance for optimizing DNS-over-TCP are 272 provided by [RFC5966], [I-D.ietf-dnsop-5966bis]. 274 4. Usage Profiles 276 This protocol provides flexibility to accommodate several different 277 use cases. Two usage profiles are defined here to identify specific 278 design points in performance and privacy. Other profiles are 279 possible but are outside the scope of this document. 281 4.1. Opportunistic Privacy Profile 283 For opportunistic privacy, analogous to SMTP opportunistic encryption 284 [RFC7435] one does not require privacy, but one desires privacy when 285 possible. 287 With opportunistic privacy, a client might learn of a TLS-enabled 288 recursive DNS resolver from an untrusted source (such as DHCP while 289 roaming), it might or might not validate the TLS certificate. These 290 choices maximize availability and performance, but they leave the 291 client vulnerable to on-path attacks that remove privacy. 293 Opportunistic privacy can be used by any current client, but it only 294 provides guaranteed privacy when there are no on-path active 295 attackers. 297 4.2. Pre-Deployed Profile 299 For pre-deployed privacy, the DNS client has one or more trusted 300 recursive DNS providers. This profile provides strong privacy 301 guarantees to the user. 303 With pre-deployed privacy, a client retains a copy of the TLS 304 certificate (and/or other authentication credentials as appropriate) 305 and IP address of each provider. The client will only use DNS 306 servers for which this information has been pre-configured. The 307 possession of a trusted, pre-deployed TLS certificate allows the 308 client to detect person-in-the-middle and downgrade attacks. 310 With pre-deployed privacy, the DNS client MUST signal to the user 311 when none of the designated DNS servers are available, and MUST NOT 312 provide DNS service until at least one of the designated DNS servers 313 becomes available. 315 The designated DNS provider may be temporarily unavailable when 316 configuring a network. For example, for clients on networks that 317 require authentication through web-based login, such authentication 318 may rely on DNS interception and spoofing. Techniques such as those 319 used by DNSSEC-trigger [dnssec-trigger] MAY be used during network 320 configuration, with the intent to transition to the designated DNS 321 provider after authentication. The user MUST be alerted that the DNS 322 is not private during such bootstrap. 324 Methods for pre-deployment of the designated DNS provider are outside 325 the scope of this document. In corporate settings, such information 326 may be provided at system installation, for instance within the 327 authenticated DHCP exchange [RFC3118]. 329 5. Performance Considerations 331 DNS-over-TLS incurs additional latency at session startup. It also 332 requires additional state (memory) and increased processing (CPU). 334 1. Latency: Compared to UDP, DNS-over-TCP requires an additional 335 round-trip-time (RTT) of latency to establish a TCP connection. 336 TCP Fast Open [RFC7413] can eliminate that RTT when information 337 exists from prior connections. The TLS handshake adds another 338 two RTTs of latency. Clients and servers should support 339 connection keepalive (reuse) and out-of-order processing to 340 amortize connection setup costs. Fast TLS connection resumption 341 [RFC5077] further reduces the setup delay and avoids the DNS 342 server keeping per-client session state. TLS False Start 343 [draft-ietf-tls-falsestart] can also lead to a latency reduction 344 in certain situations. 346 2. State: The use of connection-oriented TCP requires keeping 347 additional state at the server in both the kernel and 348 application. The state requirements are of particular concern on 349 servers with many clients, although memory-optimized TLS can add 350 only modest state over TCP. Smaller timeout values will reduce 351 the number of concurrent connections, and servers can 352 preemptively close connections when resource limits are exceeded. 354 3. Processing: Use of TLS encryption algorithms results in slightly 355 higher CPU usage. Servers can choose to refuse new DNS-over-TLS 356 clients if processing limits are exceeded. 358 4. Number of connections: To minimize state on DNS servers and 359 connection startup time, clients SHOULD minimize creation of new 360 TCP connections. Use of a local DNS request aggregator (a 361 particular type of forwarder) allows a single active DNS-over-TLS 362 connection from any given client computer to its server. 363 Additional guidance can be found in [I-D.ietf-dnsop-5966bis]. 365 A full performance evaluation is outside the scope of this 366 specification. A more detailed analysis of the performance 367 implications of DNS-over-TLS (and DNS-over-TCP) is discussed in 368 [tdns] and [I-D.ietf-dnsop-5966bis]. 370 6. IANA Considerations 372 IANA is requested to add the following value to the "Service Name and 373 Transport Protocol Port Number Registry" registry in the System 374 Range. The registry for that range requires IETF Review or IESG 375 Approval [RFC6335] and such a review has been requested using the 376 Early Allocation process [RFC7120] for the well-known TCP port in 377 this document. 379 We further recommend that IANA reserve the same port number over UDP 380 for the proposed DNS-over-DTLS protocol [draft-ietf-dprive-dnsodtls]. 382 Service Name domain-s 383 Transport Protocol(s) TCP/UDP 384 Assignee IESG 385 Contact TBD 386 Description DNS query-response protocol run over TLS 387 Reference This document 389 7. Design Evolution 391 [Note to RFC Editor: please do not remove this section prior to 392 publication as it may be useful to future Foo-over-TLS efforts] 394 Earlier versions of this document proposed an upgrade-based approach 395 to establishing a TLS session. The client would signal its interest 396 in TLS by setting a "TLS OK" bit in the EDNS0 flags field. A server 397 would signal its acceptance by responding with the TLS OK bit set. 399 Since we assume the client doesn't want to reveal (leak) any 400 information prior to securing the channel, we proposed the use of a 401 "dummy query" that clients could send for this purpose. The proposed 402 query name was STARTTLS, query type TXT, and query class CH. 404 The TLS OK signaling approach has both advantages and disadvantages. 405 One important advantage is that clients and servers could negotiate 406 TLS. If the server is too busy, or doesn't want to provide TLS 407 service to a particular client, it can respond negatively to the TLS 408 probe. An ancillary benefit is that servers could collect 409 information on adoption of DNS-over-TLS (via the TLS OK bit in 410 queries) before implementation and deployment. Another anticipated 411 advantage is the expectation that DNS-over-TLS would work over port 412 53. That is, no need to "waste" another port and deploy new firewall 413 rules on middleboxes. 415 However, at the same time, there was uncertainty whether or not 416 middleboxes would pass the TLS OK bit, given that the EDNS0 flags 417 field has been unchanged for many years. Another disadvantage is 418 that the TLS OK bit may make downgrade attacks easy and 419 indistinguishable from broken middleboxes. From a performance 420 standpoint, the upgrade-based approach had the disadvantage of 421 requiring 1xRTT additional latency for the dummy query. 423 Following this proposal, DNS-over-DTLS was proposed separately. DNS- 424 over-DTLS claimed it could work over port 53, but only because a non- 425 DTLS server interprets a DNS-over-DTLS query as a response. That is, 426 the non-DTLS server observes the QR flag set to 1. While this 427 technically works, it seems unfortunate and perhaps even undesirable. 429 DNS over both TLS and DTLS can benefit from a single well-known port 430 and avoid extra latency and mis-interpreted queries as responses. 432 8. Implementation Status 434 [Note to RFC Editor: please remove this section and reference to RFC 435 6982 prior to publication.] 437 This section records the status of known implementations of the 438 protocol defined by this specification at the time of posting of this 439 Internet-Draft, and is based on a proposal described in RFC 6982. 440 The description of implementations in this section is intended to 441 assist the IETF in its decision processes in progressing drafts to 442 RFCs. Please note that the listing of any individual implementation 443 here does not imply endorsement by the IETF. Furthermore, no effort 444 has been spent to verify the information presented here that was 445 supplied by IETF contributors. This is not intended as, and must not 446 be construed to be, a catalog of available implementations or their 447 features. Readers are advised to note that other implementations may 448 exist. 450 According to RFC 6982, "this will allow reviewers and working groups 451 to assign due consideration to documents that have the benefit of 452 running code, which may serve as evidence of valuable experimentation 453 and feedback that have made the implemented protocols more mature. 454 It is up to the individual working groups to use this information as 455 they see fit". 457 8.1. Unbound 459 The Unbound recursive name server software added support for DNS- 460 over-TLS in version 1.4.14. The unbound.conf configuration file has 461 the following configuration directives: ssl-port, ssl-service-key, 462 ssl-service-pem, ssl-upstream. See 463 https://unbound.net/documentation/unbound.conf.html. 465 8.2. ldns 467 Sinodun Internet Technologies has implemented DNS-over-TLS in the 468 ldns library from NLnetLabs. This also gives DNS-over-TLS support to 469 the drill DNS client program. Patches available at https:// 470 portal.sinodun.com/stash/projects/TDNS/repos/dns-over-tls_patches/ 471 browse. 473 8.3. digit 475 The digit DNS client from USC/ISI supports DNS-over-TLS. Source code 476 available at http://www.isi.edu/ant/software/tdns/index.html. 478 8.4. getdns 480 The getdns API implementation supports DNS-over-TLS. Source code 481 available at https://getdnsapi.net. 483 9. Security Considerations 485 Use of DNS-over-TLS is designed to address the privacy risks that 486 arise out of the ability to eavesdrop on DNS messages. It does not 487 address other security issues in DNS, and there are a number of 488 residual risks that may affect its success at protecting privacy: 490 1. There are known attacks on TLS, such as person-in-the-middle and 491 protocol downgrade. These are general attacks on TLS and not 492 specific to DNS-over-TLS; please refer to the TLS RFCs for 493 discussion of these security issues. Clients and servers MUST 494 adhere to the TLS implementation recommendations and security 495 considerations of [RFC7525]. DNS clients keeping track of 496 servers known to support TLS (i.e., "pinning") enables clients to 497 detect downgrade attacks. For servers with no connection history 498 and no apparent support for TLS, clients depending on their 499 Privacy Profile and privacy requirements may choose to (a) try 500 another server when available, (b) continue without TLS, or (c) 501 refuse to forward the query. 503 2. Middleboxes [RFC3234] are be present in some networks and have 504 been known to interfere with normal DNS resolution. Use of a 505 designated port for DNS-over-TLS should avoid such interference. 506 In general, clients that attempt TLS and fail can either fall 507 back on unencrypted DNS, or wait and retry later, depending on 508 their Privacy Profile and privacy requirements. 510 3. Any protocol interactions prior to the TLS handshake are 511 performed in the clear and can be modified by a person-in-the- 512 middle attacker. For this reason, clients MAY discard cached 513 information about server capabilities advertised prior to the 514 start of the TLS handshake. 516 4. This document does not itself specify ideas to resist known 517 traffic analysis or side channel leaks. Even with encrypted 518 messages, a well-positioned party may be able to glean certain 519 details from an analysis of message timings and sizes. Clients 520 and servers may consider the use of a padding method to address 521 privacy leakage due to message sizes [I-D.edns0-padding] 523 10. Contributing Authors 525 The below individuals contributed significantly to the draft. The 526 RFC Editor prefers a maximum of 5 names on the front page, and so we 527 have listed additional authors in this section. 529 Sara Dickinson 530 Sinodun Internet Technologies 531 Magdalen Centre 532 Oxford Science Park 533 Oxford OX4 4GA 534 UK 535 Email: sara@sinodun.com 536 URI: http://sinodun.com 538 11. Acknowledgments 540 The authors would like to thank Stephane Bortzmeyer, John Dickinson, 541 Daniel Kahn Gillmor, Brian Haberman, Kim-Minh Kaplan, Bill Manning, 542 George Michaelson, Eric Osterweil, and Glen Wiley for reviewing this 543 Internet-draft. They also thank Nikita Somaiya for early work on 544 this idea. 546 Work by Zi Hu, Liang Zhu, and John Heidemann on this document is 547 partially sponsored by the U.S. Dept. of Homeland Security (DHS) 548 Science and Technology Directorate, HSARPA, Cyber Security Division, 549 BAA 11-01-RIKA and Air Force Research Laboratory, Information 550 Directorate under agreement number FA8750-12-2-0344, and contract 551 number D08PC75599. 553 12. References 555 12.1. Normative References 557 [I-D.ietf-dnsop-5966bis] 558 Dickinson, J., Dickinson, S., Bellis, R., Mankin, A., and 559 D. Wessels, "DNS Transport over TCP - Implementation 560 Requirements", draft-ietf-dnsop-5966bis-02 (work in 561 progress), July 2015. 563 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 564 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 565 . 567 [RFC1035] Mockapetris, P., "Domain names - implementation and 568 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, 569 November 1987, . 571 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 572 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ 573 RFC2119, March 1997, 574 . 576 [RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig, 577 "Transport Layer Security (TLS) Session Resumption without 578 Server-Side State", RFC 5077, DOI 10.17487/RFC5077, 579 January 2008, . 581 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 582 (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/ 583 RFC5246, August 2008, 584 . 586 [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. 587 Cheshire, "Internet Assigned Numbers Authority (IANA) 588 Procedures for the Management of the Service Name and 589 Transport Protocol Port Number Registry", BCP 165, 590 RFC 6335, DOI 10.17487/RFC6335, August 2011, 591 . 593 [RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code 594 Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, 595 January 2014, . 597 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 598 "Recommendations for Secure Use of Transport Layer 599 Security (TLS) and Datagram Transport Layer Security 600 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, 601 May 2015, . 603 12.2. Informative References 605 [I-D.confidentialdns] 606 Wijngaards, W., "Confidential DNS", 607 draft-wijngaards-dnsop-confidentialdns-03 (work in 608 progress), March 2015, . 611 [I-D.edns-tcp-keepalive] 612 Wouters, P., Abley, J., Dickinson, S., and R. Bellis, "The 613 edns-tcp-keepalive EDNS0 Option", 614 draft-ietf-dnsop-edns-tcp-keepalive-02 (work in progress), 615 July 2015, . 618 [I-D.edns0-padding] 619 Mayrhofer, A., "The EDNS(0) Padding Option", 620 draft-mayrhofer-edns0-padding-01 (work in progress), 621 August 2015, . 624 [I-D.ipseca] 625 Osterweil, E., Wiley, G., Okubo, T., Lavu, R., and A. 626 Mohaisen, "Opportunistic Encryption with DANE Semantics 627 and IPsec: IPSECA", draft-osterweil-dane-ipsec-03 (work in 628 progress), July 2015, 629 . 632 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, DOI 10.17487/ 633 RFC2818, May 2000, 634 . 636 [RFC3118] Droms, R. and W. Arbaugh., Ed., "Authentication for DHCP 637 Messages", RFC 3118, DOI 10.17487/RFC3118, June 2001, 638 . 640 [RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and 641 Issues", RFC 3234, DOI 10.17487/RFC3234, February 2002, 642 . 644 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 645 Rose, "DNS Security Introduction and Requirements", 646 RFC 4033, DOI 10.17487/RFC4033, March 2005, 647 . 649 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 650 Housley, R., and W. Polk, "Internet X.509 Public Key 651 Infrastructure Certificate and Certificate Revocation List 652 (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, 653 . 655 [RFC5966] Bellis, R., "DNS Transport over TCP - Implementation 656 Requirements", RFC 5966, DOI 10.17487/RFC5966, 657 August 2010, . 659 [RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication 660 of Named Entities (DANE) Transport Layer Security (TLS) 661 Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, 662 August 2012, . 664 [RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an 665 Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, 666 May 2014, . 668 [RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP 669 Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014, 670 . 672 [RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection 673 Most of the Time", RFC 7435, DOI 10.17487/RFC7435, 674 December 2014, . 676 [RFC7626] Bortzmeyer, S., "DNS Privacy Considerations", RFC 7626, 677 DOI 10.17487/RFC7626, August 2015, 678 . 680 [dempsky-dnscurve] 681 Dempsky, M., "DNSCurve", draft-dempsky-dnscurve-01 (work 682 in progress), August 2010, 683 . 685 [dnssec-trigger] 686 NLnet Labs, "Dnssec-Trigger", May 2014, 687 . 689 [draft-ietf-dprive-dnsodtls] 690 Reddy, T., Wing, D., and P. Patil, "DNS over DTLS 691 (DNSoD)", draft-ietf-dprive-dnsodtls-01 (work in 692 progress), June 2015, . 695 [draft-ietf-tls-falsestart] 696 Moeller, B. and A. Langley, "Transport Layer Security 697 (TLS) False Start", draft-ietf-tls-falsestart-00 (work in 698 progress), November 2014, 699 . 701 [tdns] Zhu, L., Hu, Z., Heidemann, J., Wessels, D., Mankin, A., 702 and N. Somaiya, "T-DNS: Connection-Oriented DNS to Improve 703 Privacy and Security", Technical report ISI-TR-688, 704 February 2014, . 707 Authors' Addresses 709 Zi Hu 710 USC/Information Sciences Institute 711 4676 Admiralty Way, Suite 1133 712 Marina del Rey, CA 90292 713 USA 715 Phone: +1 213 587-1057 716 Email: zihu@usc.edu 718 Liang Zhu 719 USC/Information Sciences Institute 720 4676 Admiralty Way, Suite 1133 721 Marina del Rey, CA 90292 722 USA 724 Phone: +1 310 448-8323 725 Email: liangzhu@usc.edu 727 John Heidemann 728 USC/Information Sciences Institute 729 4676 Admiralty Way, Suite 1001 730 Marina del Rey, CA 90292 731 USA 733 Phone: +1 310 822-1511 734 Email: johnh@isi.edu 736 Allison Mankin 737 Verisign Labs 738 12061 Bluemont Way 739 Reston, VA 20190 741 Phone: +1 703 948-3200 742 Email: amankin@verisign.com 743 Duane Wessels 744 Verisign Labs 745 12061 Bluemont Way 746 Reston, VA 20190 748 Phone: +1 703 948-3200 749 Email: dwessels@verisign.com 751 Paul Hoffman 752 ICANN 754 Email: paul.hoffman@icann.org